The casting of metallic parts is a well known manufacturing technique. Metal casting is typically accomplished by introducing a molten, generally non-ferrous, metal (e.g., aluminum) into a closed die (mold). After metal introduction, the cast part is cooled and the formed part is removed from the mold.
Casting can be used to form parts of complex shape and, therefore, is commonly used in the automotive industry. For example, aluminum casting has become increasingly used to manufacture vehicle engine parts. Some of these parts may require that a cavity, port, passageway, and/or other hollow area be formed therein. To that end, it is known to locate a core within a casting mold. Such cores are frequently made of sand when the casting process does not employ high clamping and metal injection pressures. The core remains in the mold during the introduction of molten metal to form the necessary hollow feature(s) within the finished part. Once the part has cooled, the part and the core are removed from the mold, and the core is subsequently removed from the part by any of various techniques known to those of skill in the art.
One difficulty associated with the use of such a core is that the core must be retained in an intended position within the mold in order to properly form the desired feature(s) in the cast part. This has proven problematic. For example, one particular problem is the tendency of such a core to move or “float” away from its proper position under the force of injected molten metal. The result of such core displacement may be a malformed feature in the cast part, such as a cavity or aperture that is partially or wholly covered by flash.
Core float and improper part formation is a problem known to occur during the casting of vehicle engine cylinder heads. For example, during a cylinder head casting operation, the complex shape of an associated exhaust port core (see FIG. 1a), its position within a cylinder head casting mold, and the nature of the mold, can result in a displacement or floating of the core during the introduction of molten metal—even in a low pressure casting operation. Such a displacement of the exhaust port core can result in, among other problems, partially formed or unformed exhaust ports (see FIG. 1b).
Producing a cylinder head with partially formed or unformed exhaust ports is obviously undesirable, as the result is either the need for additional machining or a scrap part. Therefore, it can be understood that a technique for retaining a core in proper position during a cylinder head casting operation is desirable. The present invention is directed to a device and method for such core retention.